examen linux tema 7

Descripción

Test sobre examen linux tema 7, creado por Jesus Reyes Real el 28/11/2016.
Jesus Reyes Real
Test por Jesus Reyes Real, actualizado hace más de 1 año
Jesus Reyes Real
Creado por Jesus Reyes Real hace más de 7 años
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Resumen del Recurso

Pregunta 1

Pregunta
Compression on a file works by:
Respuesta
  • Removing redundant information
  • Eliminating gaps within the file
  • Storing most of the data on removable media and just leaving a pointer
  • Consolidating multiple files into one
  • Removing the high order bit from each byte

Pregunta 2

Pregunta
In general, for which of the following would you want to use lossless compression?
Respuesta
  • A log file
  • A movie
  • A JPEG image
  • An mp3 audio file
  • An encrypted email

Pregunta 3

Pregunta
Lossy compression: (choose three)
Respuesta
  • Decompresses to an identical version as the original
  • Is often used with documents
  • Is often used with images
  • Usually results better compression than lossless
  • Sacrifices some quality

Pregunta 4

Pregunta
You type gzip myfile.tar. What happens? (choose two)
Respuesta
  • myfile.tar is removed
  • myfile.tar.gz holds a compressed version of myfile.tar
  • An error; you forgot to specify the file with –f
  • myfile.tar is unarchived into the current directory
  • An error; you forgot to pass the name of the output file

Pregunta 5

Pregunta
How would you obtain output similar to the following? compressed uncompressed ratio uncompressed_name 278168  1016950             72.6% tags
Respuesta
  • gunzip –t tags
  • file tags
  • gzip –l tags

Pregunta 6

Pregunta
Which command would you use to archive the Documents directory and compress it with bzip2 compression?
Respuesta
  • tar –czf documents.tbz Documents
  • tar –cjf Documents
  • tar –fzc Documents documents.tbz
  • tar –cjf documents.tbz Documents
  • tar –cf Documents documents.tbz

Pregunta 7

Pregunta
Which flag would you pass to tar in order to have it make a new archive?
Respuesta
  • –t
  • ­-c
  • –j
  • -x
  • -n

Pregunta 8

Pregunta
Which command will show what is inside the compressed tarball with a name of foo.tar.gz?
Respuesta
  • tar –tjf foo.tar.gz
  • tar –tzf foo.tar.gz
  • tar –lf foo.tar.gz
  • tar –xf foo.tar.gz
  • tar –tf foo.tar.gz

Pregunta 9

Pregunta
In the command tar –cvjf foo.tbz a b c, what are a, b, and c?
Respuesta
  • File names to be added to the archive
  • Matching operators; anything starting with a, b, or c will be added
  • a is the directory that will be prepended to files; b and c are files inside it
  • Extra flags passed to tar
  • Nothing; ­cvjf only expects one parameter

Pregunta 10

Pregunta
Given the command tar –cvjf homedirs.tbz /home, which of the following are true? (choose two)
Respuesta
  • The /home directory will be restored with the contents of homedirs.tbz
  • Only files starting with /home will be extracted from the archive
  • The command will print out each filename as it is processed
  • Files that are present in the archive might overwrite files in /home
  • The output file will be compressed

Pregunta 11

Pregunta
You archived your users’ directories into a file called backup.tar.gz. You then view the archive and see the filenames follow this convention: home/username/somefile
Respuesta
  • How will you extract just the files for the user called fred?
  • tar –tzf /home/fred < backup.tar.gz
  • tar –tjf backup.tar.gz /home/fred
  • tar –xjf backup.tar.gz home/fred/
  • tar –xzf backup.tar.gz home/fred/

Pregunta 12

Pregunta
Which of the following commands will create a zipfile with the contents of your Documents directory?
Respuesta
  • zip –cf mydocs.zip Documents
  • zip –c mydocs.zip Documents
  • zip -­r mydocs.zip Documents
  • zip mydocs.zip Documents
  • zip –f mydocs.zip Documents

Pregunta 13

Pregunta
Given a file called documents.zip, how can you see what’s in it without extracting the files?
Respuesta
  • showzip documents.zip
  • zip –lf documents.zip
  • zip –l documents.zip
  • unzip –list documents.zip
  • unzip –l documents.zip

Pregunta 14

Pregunta
Given a file called documents.zip, how can you extract just the files under ProjectX?
Respuesta
  • zip –x documents.zip ProjectX
  • unzip documents.zip | grep ProjectX
  • unzip –t documents.zip ProjectX
  • unzip documents.zip ProjectX
  • unzip documents.zip ProjectX/*

Pregunta 15

Pregunta
You try to compress a file that is already compressed. Which of the following statements is true?
Respuesta
  • The file will not be compressed any further than it already was
  • The compression algorithm needs to be set to the “currently compressed” mode for it to be compressed further
  • The file will actually be uncompressed
  • The file will be deleted
  • The file changed while you were compressing it

Pregunta 16

Pregunta
Which of the following commands can be used to compress a file? (choose three)
Respuesta
  • bunzip2
  • bzip2
  • gzip
  • cat
  • zip

Pregunta 17

Pregunta
The three main modes of tar are: (choose three)
Respuesta
  • Copy
  • List
  • Compress
  • Create
  • Extract

Pregunta 18

Pregunta
In the command tar –czf foo.tar.gz bar, what is the purpose of the f flag?
Respuesta
  • Tells tar to read from the file that follows the flag
  • Tells tar to print the name of each file as it is processed
  • Tells tar to copy only files, and not directories
  • Specifies extra compression is to be used
  • Tells tar to write to the file that follows the flag

Pregunta 19

Pregunta
Which two commands do the same thing? (choose two)
Respuesta
  • tar –czf foo.tar.gz foo
  • tar –c foo | gzip > foo.tar.gz
  • tar –xzf foo.tar.gz
  • tar –x foo | gzip
  • tar –tzf foo.tar.gz

Pregunta 20

Pregunta
The _____ command is normally executed daily to update the database of all files that are on the system.
Respuesta
  • updatedb
  • search
  • locate
  • find
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